Huntingdon. - Area, 900 square miles; population in
1880, 33,954. Through the middle of the large county runs, north north-eastward,
the deepest synclinal trough in the State, and in its deepest portion
(on the Bedford-Fulton line) has been preserved the Broad-Top semi-bituminous
coal field, on a mountain surrounded by a mountain of No. X (Pocono)
called Terrace mountain on the western side, and Sideling hill on
the eastern; the two uniting in a knob (2000` A.T.) overlooking the
Juniata valley at Huntingdon. The trough rises slowly northward bringing
up successive curves of VIII, VII, VI, V, and finally IV in the Seven
Mountains on the Clinton line. The east side of the trough being nearly
vertical, the outcrops are straight and narrow, No. IV forming Standing
Stone mountain; the west side of the trough being a very gentle slope,
the outcrops are broad, and minor rolls in it produce the spurs of
sandstone (VII) and limestone (VI) of Warrior’s Ridge, crowned by
pulpit rocks, through which the Juniata cuts its picturesque gorge,
4 miles long, between Huntingdon, and Petersburgh, in which the nearly
horizontal sandstone is seen overlying the limestone. Corresponding
to the spurs of the ridge are spurs in Tussey mountain; and between
the two sets of spurs, in the broad valley of Shaver’s creek and the
heads of Mill creek, sweeps the zigzagged outcrop of the fossil iron
ore beds of No. V, mined at Greenwood furnace in Jackson Township.
Tussey mountain is gapped by the Little Juniata at Spruce creek, and
by the main Juniata at Water Street, and then, after one anticlinal
spur, runs straight on southward to Bedford county, carrying on its
lower slope the block ore and fossil ore beds mined at Barree forge,
at Marklesburg, and at points further south. No fossil ore is mined
along the Standing-stone outcrop south of Greenwood, nor in Hare’s
valley. The south end of Kishicoquillis valley, with its slate (III)
and limestone (II) just enters the county. The Jack’s mountain anticlinal
arch is cut through between Mapleton and Mt. Union, and here the vertical
Oriskany outcrop (VII) has been extensively quarried for glass-sand.
Jack’s mountain runs on south to Three Springs, where a fine fault
has been pictured and described in Report F. The No. VIII valley of
Aughwick creek separates Jack’s from Black-Log mountain, along the
west foot of which the Marcellus brown hematite ore (VIII) and the
Clinton fossil ore (V) are mined at many points, especially at Orbisonia,
where Black-Log creek makes a gap, through which runs a downthrow
fault of 90`, mapped and described in Report F. The Black-Log anticlinal
brings up III and II in a straight valley (2 miles wide) between Black-Log
and Shade mountains, which crosses the county. East of Shade mountain
runs the straight Tuscarora valley of V, VI, VII, and VIII, with traces
of fossil ore, and bounded on the east county line by Tuscarora Mountain.
Black-Log mountain south of Orbisonia is shivered by numerous very
small cross faults, discovered in mining the fossil ore. On the summit
of the mountain is a very remarkable deposit of brown hematite ore,
connected with one of these faults. The north-west corner of the county
covers the north end of Canoe Valley and the wide limestone (II) valley
of Spruce Creek and Warrior Mark with numerous deposits of brown hematite
ore. Tussey Mountain is faulted in the Spruce Creek gap, the fault
being cut in the P.R.R. tunnel. The Juniata cuts a remarkable gorge
lengthwise in the middle red member of IV, separating the ridge of
White Medina from the higher ridge of Oneida, a very rare occurrence,
and wildly picturesque. The anticlinal of Canoe Valley, between Tussey
and Canoe mountains, is excessively steep and compressed, with a double
fold along its crest line, and the Cambro-Silurian limestone strata
(No.II) are thicker here than anywhere else in the State; for the
extensive topographical survey of this region by Mr.Sanders (see the
contoured sheets in Atlas to Report T) resulted in a measurement of
(1) an Upper limestone series, 5400`; (2) Middle white
limestone beds, 40`; and (3) Lower limestone series (including
perhaps some beds properly belonging to the Potsdam formation No.
I) 1160`, a total of 660 feet. As Canoe mountain ends in a synclinal
knob at the Little Juniata River, the steep west dips of Canoe Valley
give place to the gentle east dips of Sinking Creek valley up to Tyrone
forges, where there is a fault, and the rocks immediately descend
vertically westward in Bald Eagle mountain. Three miles north of the
gap this mountain is faulted (1500`) crosswise, twice, so as each
time to shift the terrace of Oneida sandstone into line with the crest
of White Medina sandstone, making a beautiful piece of topography,
mapped by Mr. Harden. (See Report T3.) The upper Medina
is about 1170`, the lower red beds 520`, and the Oneida 1320` thick.
The gorge of Little Trough Creek, splitting Rocky Ridge at the north
end of the East Broad-Top coal basin, is one of the most picturesque
bits of scenery in the State, and is of considerable geological importance.
The limestone strata in No. XI red shale around Broad-Top is also
most interesting as the beginning in Pennsylvania of the great sub-Carboniferous
limestone formation of the Southern and Western States. The exposure
of a group of small coal beds in the E.B.T.R.R. tunnel through Sideling
hill (described in Report F) has thrown a clear light upon the nature
and value of the numerous so-called discoveries of workable coal crops
in the Pocono sandstone No. X, in various parts of Pennsylvania, none
of which have ever answered the expectations of explorers. The group
represents, however, the valuable sub-Conglomerate coal system
of Virginia, Tennessee, and Alabama. (See Report T4.)
From: A geological hand atlas of the sixty-seven
counties of Pennsylvania :embodying the results of the field work
of the survey, from 1874 to 1884. By J. P. Lesley. (Report of
progress (Geological Survey of Pennsylvania), v. X ) Harrisburg, PA
: Board of commissioners for the second geological survey, 1885.
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